Low water stannous fluoride plus zinc citrate dentifrice with improved stability, rheology, and efficacy

ABSTRACT

A dentifrice composition having a low water phase comprising effective amounts of polyphosphate and ionic active ingredients.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/503,801, filed Apr. 24, 2012, which is a national stage entry under35 U.S.C. § 371 of International Patent Application No. PCT/US09/62452,filed on 29 Oct. 2009, the contents of which are incorporated herein byreference.

The present embodiments relate to dentifrice compositions. Inparticular, the present embodiments relate to dentifrice compositionshaving a low water phase comprising effective amounts of polyphosphateand ionic active ingredients. The ionic active ingredients may includefluoride ions and metal ions such as stannous and zinc ion source.

BACKGROUND

Polyphosphates and ionic active ingredients have been used indentifrices to promote oral health. Polyphosphates are known anti-tartaragents that help retard calculus formation. Metal ions such as stannousand zinc ions are known to be effective anti-microbial agents. Thesemetal ions provide anti-gingivitis and anti-plaque benefits and may alsoimprove breath and reduce sensitivity. Stannous fluoride has been usedin dentistry since the 1950's as a fluoride source to prevent dentalcaries. Similarly, zinc citrate has been shown to have anti-plaque,anti-gingivitis and anti-tartar efficacy. In addition, zinc has alsoshown its efficacy as an anti-malodor agent.

While such actives have previously been used in dentifrices, for severalreasons it has proven challenging to provide these actives together in astable single phase. Once such technical problem is to preserve thebioavailability of stannous ions and maximize the chemical stability ofthe stannous ion source. Certain polyphosphates are unstable in highaqueous systems. Such polyphosphates in an aqueous system aresusceptible to hydrolysis unless they are present at a high pH, which isnot compatible with high stannous availability. Stannous fluoride tendsto precipitate stannous ions in aqueous environments, thereby reducingthe efficacy of the stannous ions in the oral care composition.Additionally, the polyphosphates react with ionic fluoride in oralcompositions at ambient temperature to produce monofluorophosphate ionsand alter the pH of the composition. This reaction compromises theefficacy of the oral composition and its ability to provide stable ionicfluoride and polyphosphate to the oral surfaces.

Other attempts to provide such efficacious dentifrice compositions havereduced the amount of water present in the composition. Reducing theamount of water would theoretically reduce or eliminate the stabilityissues associated with the fluoride, polyphosphate and other ionicactives. However, reducing the level of water, and optionally replacingsome or all of the removed water with a humectant, creates problems inobtaining acceptable rheology and thickening properties in thecomposition. When water, which is a highly polar solvent, is removed,conventional thickening agents such as carboxymethylcellulose (“CMC”)tend to inadequately gel up. Attempts to reduce water content indentifrice compositions have included the dentifrices described in,e.g., EP 0 638 307 B1; U.S. Pat. Nos. 4,647,451; and 5,670,137. Suchknown formulations have been shown to exhibit progressive thickeningover time, which prolongs the time period or even prevents thedentifrice from reaching a rheological steady state. Ideally, dentifriceformulations need to reach a steady state for consumer acceptance withintwo weeks. If a formulation routinely increases in viscosity over time,dispensing of the formulation will become difficult, which will likelyresult in consumer dissatisfaction.

U.S. Pat. No. 6,696,045 discloses dentifrice compositions comprising asingle low water phase comprising polyphosphate and ionic activeingredients. Although compositions comprising glass H polyphosphate,which has a long chain of about 21 phosphate groups, and sodium orstannous fluoride are disclosed, with the sodium fluoride beingoptionally combined with zinc citrate and the stannous fluoride beingoptionally combined with zinc lactate, there is no disclosure of how tocombine stannous, fluoride and zinc salts in a low water composition incombination with short chain length polyphosphates in a low water singlephase system.

U.S. Pat. No. 5,578,293 discloses dentifrice compositions comprising ahigh water phase comprising polyphosphate and ionic active ingredients,including stannous ions.

U.S. Pat. No. 5,487,906 also discloses dentifrice compositionscomprising a high water phase comprising polyphosphate and ionic activeingredients, including stannous ions.

Other attempts to provide dentifrice compositions having these activesin efficacious amounts involved the use of dual compartmented packagingwherein the reactive ingredients are physically separated until the timeof brushing. (See, e.g., WO98/22079, “Dentifrice Compositions ContainingPolyphosphate and Fluoride.”) However, such dual-compartmented packagesare typically considerably more expensive than the conventional laminatetubes that have been used for many years to contain and dispensedentifrices. They also may be problematic in terms of ease of consumeruse and uniform dispensing of approximately equal amounts of eachcomposition during each consumer use. Therefore it remains desirable toprovide single phase compositions that can be packaged in conventionallaminate squeeze tubes.

The description herein of certain advantages and disadvantages of knowncompositions, methods, and apparatus is not intended to limit the scopeof the embodiments to their exclusion (or inclusion, as the case maybe). Indeed, certain embodiments may include one or more knowncompounds, methods, or apparatus without suffering from theafore-mentioned disadvantages.

BRIEF SUMMARY

There is a need in the art to provide dentifrice compositions that caneffectively combine sources of stannous, fluoride, and zinc ions incombination with a polyphosphate in a low water single phase system thathas efficacious delivery of water-unstable actives and/or actives thatare reactive with respect to each other in a single phase. There is alsoa need in the art to provide low water single phase dentifricecompositions that have an improved rheological profile, and inparticular have a stable rheology that effectively reduces or eliminatesprogressive thickening of the composition over time which in turnprovides a composition that can effectively be dispensed over the periodof its shelf life.

In a first aspect, the embodiments described herein provide a dentifricecomposition comprising in a single phase: an orally acceptable vehicle;a source of fluoride ions; a source of stannous ions; a source of zincions; and at least one polyphosphate salt selected from the groupconsisting of inorganic polyphosphate salts that have equal to or lessthan three phosphorous atoms; wherein the dentifrice composition has atotal water content of less than about 10% based on the weight of thecomposition.

In a second aspect, the embodiments described herein provide adentifrice composition comprising, in a single phase, an orallyacceptable vehicle, the vehicle including a thickening agent comprisinga polymer system comprising, in combination, a cross-linkedpolyvinylpyrrolidone and a gum, wherein the dentifrice composition has atotal water content of less than about 10% based on the weight of thecomposition.

In a third aspect, the embodiments described herein provide a method forthe treatment and prevention of bacterial plaque accumulation and/or forthe prevention of erosion or demineralization comprising: administeringto the oral cavity the dentifrice composition described above.

In a fourth aspect, the embodiments described herein provide a methodfor the manufacture of a dentifrice composition, the method comprising:providing a source of stannous ions; mixing the source of stannous ionswith an aqueous buffer system adapted to chelate the stannous ions in apremix formed thereby; and combining the premix with at least one activecomponent and an orally acceptable vehicle of the dentifricecomposition.

As will be demonstrated herein, the preferred embodiments can provide adentifrice that provides multiple therapeutic benefits by combiningstannous ions and fluoride ions, e.g. as stannous fluoride, zinc ions,e.g. as zinc citrate, and polyphosphates, e.g. in the form oftetrasodium pyrophosphate/sodium tripolyphosphate. The use of aparticular buffer system can stabilize the stannous ions in the presenceof the zinc ions and polyphosphates, and leave the stannous ions activein the single phase low water composition for effective anti-microbialaction when used for cleaning the teeth.

The preferred embodiments of the present invention also can provide adentifrice formulation having a stabilized stannous ion source and apolyphosphate, for example tetrasodium pyrophosphate and/or sodiumtripolyphosphate, in a single tube.

The preferred embodiments of the present invention also can provide alow water dentifrice system combining, in a single tube, stannousfluoride, zinc citrate and polyphosphates, in particular having aphosphorous atom of equal to or less than 3, for example tetrasodiumpyrophosphate and sodium tripolyphosphate, in a single phase system thatprovides bioavailable tin, zinc, fluoride and polyphosphate to the oralsurfaces.

The preferred embodiments of the present invention also may provide alow water single phase dentifrice system having a stable rheology thatdoes not tend to progressively thicken over time, but instead thickensquickly, for example within a few days of manufacture, and reaches astable viscosity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between Brookfield viscosityand time (days) for the dentifrice composition of Formula B in theexamples.

FIG. 2 is a graph showing the relationship between Brookfield viscosityand time (days) for a comparative dentifrice composition.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following definitions and non-limiting guidelines should beconsidered in reviewing the description of the invention set forthherein. The headings (such as “Background” and “Summary”) andsub-headings used herein are intended only for general organization oftopics within the disclosure of the invention, and are not intended tolimit the disclosure of the invention or any aspect thereof. Inparticular, subject matter disclosed in the “Background” may includeaspects of technology within the scope of the invention, and may notconstitute a recitation of prior art. Subject matter disclosed in the“Summary” is not an exhaustive or complete disclosure of the entirescope of the invention or any embodiments thereof. Classification ordiscussion of a material within a section of this specification ashaving a particular utility (e.g., as being an “active” or a “carrier”ingredient) is made for convenience, and no inference should be drawnthat the material must necessarily or solely function in accordance withits classification herein when it is used in any given composition.

All publications, patent applications, and issued patents mentionedherein are hereby incorporated in their entirety by reference. Thecitation of documents herein does not constitute an admission that thosedocuments are prior art or have any relevance to the patentability ofthe invention disclosed herein. Any discussion of the content ofdocuments cited in the Introduction is intended merely to provide ageneral summary of assertions made by the authors of the documents, anddoes not constitute an admission as to the accuracy of the content ofsuch documents.

The description and specific examples, while indicating embodiments ofthe invention, are intended for purposes of illustration only and arenot intended to limit the scope of the invention. Moreover, recitationof multiple embodiments having stated features is not intended toexclude other embodiments having additional features, or otherembodiments incorporating different combinations of the stated features.Specific examples are provided for illustrative purposes of how to makeand use the compositions and methods of this invention and, unlessexplicitly stated otherwise, are not intended to be a representationthat given embodiments of this invention have, or have not, been made ortested.

As used herein, the words “preferred” and “preferably” refer toembodiments of the invention that afford certain benefits, under certaincircumstances. However, other embodiments also may be preferred, underthe same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the invention.

As used herein, “comprising” encompasses “consisting of” and “consistingessentially of.” As used herein, the word “include,” and its variants,is intended to be non-limiting, such that recitation of items in a listis not to the exclusion of other like items that may also be useful inthe materials, compositions, devices, and methods of this invention.

As used herein, the term “about” when applied to the value for aparameter of a composition or method of this invention, indicates thatthe calculation or the measurement of the value allows some slightimprecision without having a substantial effect on the chemical orphysical attributes of the composition or method. If, for some reason,the imprecision provided by “about” is not otherwise understood in theart with this ordinary meaning, then “about” as used herein indicates apossible variation of up to 5% in the value.

All percentages used herein are by weight of the total dentifricecomposition, unless otherwise specified. The ratios used herein areweight ratios of the respective components, unless otherwise specified.All measurements are made at 25° C., unless otherwise specified.

As used throughout, ranges are used as a shorthand for describing eachand every value that is within the range. Any value within the range canbe selected as the terminus of the range.

Herein, “effective amount” means an amount of a compound or compositionsufficient to significantly induce a positive benefit, preferably anoral health benefit, but low enough to avoid serious side effects, i.e.,to provide a reasonable benefit to risk ratio, within the sound judgmentof a skilled artisan.

A dentifrice composition is a product, which in the ordinary course ofadministration, is not intentionally swallowed for purposes of systemicadministration of particular therapeutic agents, but is rather retainedin the oral cavity for a time sufficient to contact substantially all ofthe tooth surfaces and/or oral tissues for purposes of oral activity. Adentifrice composition of the present invention may be in the form of atoothpaste or dentifrice. The term “dentifrice,” as used herein, meanspaste or gel formulations unless otherwise specified. The dentifricecomposition may be in any desired form, such as deep striped, surfacestriped, multi-layered, having the gel surrounding the paste, or anycombination thereof.

The phrase “aqueous carrier” as used herein means any safe and effectivematerials for use in the compositions of the present embodiments. Suchmaterials include thickening agents, humectants, ionic activeingredients, buffering agents, anticalculus agents, abrasive polishingmaterials, peroxide sources, alkali metal bicarbonate salts,surfactants, titanium dioxide, coloring agents, flavor systems,sweetening agents, antimicrobial agents, herbal agents, desensitizingagents, stain reducing agents, and mixtures thereof.

The embodiments described herein relate to a dentifrice compositionhaving a phase with a low water content and containing an orallyacceptable vehicle, a source of fluoride ions, a source of stannousions, a source of zinc ions, and at least one polyphosphate salt. Thepolyphosphate salt may be inorganic polyphosphate salts which have threeor less phosphorous atoms. The dentifrice composition may have a totalwater content of less than about 10% based on the weight of thecomposition. The dentifrice composition preferably has a total watercontent of less than about 6% based on the weight of the composition.

The vehicle may include a thickening agent comprising a polymer systemcomprising at least one of a cross-linked polyvinylpyrrolidone and agum. The thickening agent may comprise, in combination, the cross-linkedpolyvinylpyrrolidone and the gum. The gum may comprise xanthan gum. Thegum may comprise from 0.1 to 0.5 wt % of the composition, preferablyfrom 0.2 to 0.3 wt of the composition.

The cross-linked polyvinylpyrrolidone may comprise a homopolymer ofN-vinyl-2-pyrrolidone. The cross-linked polyvinylpyrrolidone maycomprise from 0.05 to 15 wt % of the composition, preferably from 0.75to 1.25 wt % of the composition.

The at least one polyphosphate may be selected from the group consistingof an alkali metal salt of a pyrophosphate or a tripolyphosphate,preferably the at least one polyphosphate is selected from the groupconsisting of tetrasodium pyrophosphate or sodium tripolyphosphate. Theat least one polyphosphate may comprise a mixture of tetrasodiumpyrophosphate and sodium tripolyphosphate, and preferably the mixture oftetrasodium pyrophosphate and sodium tripolyphosphate comprises thetetrasodium pyrophosphate and sodium tripolyphosphate in about a 2:3weight ratio. The at least one polyphosphate may comprise from 1 to 10wt % of the composition, preferably from 3 to 7 wt % of the composition.

Preferably, the source of fluoride ions and the source of stannous ionscomprise stannous fluoride. Preferably, the source of zinc ionscomprises a zinc salt of an organic acid, more preferably zinc citrate.The source of zinc ions may also comprise any zinc compound including,for example, zinc oxide, zinc tartrate, zinc gluconate, and the like.

In the dentifrice composition, the thickening agent may further compriseat least one of a cellulose and a synthetic block copolymer of ethyleneoxide and propylene oxide. The composition may further comprise at leastone humectant selected from the group consisting of glycerin,polyethylene glycol, propylene glycol, and mixtures thereof.

Preferably, the composition further comprises an aqueous buffer systemfor the source of stannous ions. The buffer system preferably is adaptedto chelate the stannous ions in the composition. The buffer system maycomprise at least one of an organic acid or an alkali metal saltthereof, the organic acid preferably being citric acid. The buffersystem may comprise a mixture of citric acid and trisodium citrate. Thebuffer system may comprise from 1 to 5 wt % of the composition. Thebuffer system may be present, by weight, in an amount that is greaterthan the amount, by weight, of the source of stannous ions.

The use of the buffer system described herein is believed to reduce oreliminate precipitation of insoluble tin compounds. While not intendingon being bound by any theory of operation, the inventors believe that anaqueous buffer system, e.g. a citrate buffer system, which may beemployed as a premix for the stannous salt to chelate the stannous ions,can reduce or eliminate the precipitation of insoluble tin compounds inthe presence of zinc ions and polyphosphates in a low water dentifricecomposition.

Correspondingly, the present invention also provides a method for themanufacture of a dentifrice composition, the method comprising providinga source of stannous ions, mixing the source of stannous ions with anaqueous buffer: system adapted to chelate the stannous ions in a premixformed thereby, and combining the premix with at least one activecomponent and an orally acceptable vehicle of the dentifricecomposition.

The present invention also provides a dentifrice composition comprising,in a single phase, an orally acceptable vehicle, the vehicle including athickening agent comprising a polymer system comprising, in combination,a cross-linked polyvinylpyrrolidone and a gum, wherein the dentifricecomposition has a total water content of less than about 10% based onthe weight of the composition.

While not intending on being bound by any theory of operation, thepresent inventors believe that a particular thickening system, whichemploys a cross-linked polyvinylpyrrolidone in combination with a gum,such as xanthan gum, enables a single phase low water dentifricecomposition to achieve a viscosity that is substantially constant andthat is sufficiently low to permit the dentifrice composition readily tobe dispensed over a long shelf life. Without being bound by any theory,it is believed by the present inventors that the combination of thecross-linked polyvinylpyrrolidone with a gum, such as xanthan gum,permits time polyvinylpyrrolidone polymer thickener to be readilyhydrated in the low water system, which allows substantially completeinitial hydration of the polymer during manufacture of the dentifricecomposition. This tends to minimize subsequent hydration of the polymer,which would tend to cause the polymer to be continuously andprogressively hydrated over time subsequent to the initial manufacture,which would remove water from other raw material sources in thecomposition, resulting in progressive thickening.

While the specification concludes with claims particularly pointing outand distinctly claiming the invention, it is believed that the presentinvention will be better understood from the following description ofpreferred embodiments.

Polyphosphate Source

The present embodiments may include a polyphosphate source.Polyphosphates are known to help retard calculus formation. However, itis also known that polyphosphates with an average chain length greaterthan about 4 will also read with ionic fluoride in oral compositions atambient temperature and produce monofluorophosphate ions, in addition toaltering the pH: of the composition. This reaction may compromise theefficacy of the oral composition and its ability to provide stable ionicfluoride and polyphosphate to the oral surfaces. It also is known thatto have stable polyphosphate, the total water content and pH of thedentifrice composition should be controlled to reduce the hydrolysis ofthe polyphosphate.

A polyphosphate generally is understood to consist of two or morephosphate molecules arranged primarily in a linear configuration,although some cyclic derivatives may be present. The preferred inorganicpolyphosphate salts, which are preferably alkali metal salts, used inthe dentifrice compositions of the present invention have no more thanthree phosphorous atoms, such as a pyrophosphate, for exampletetrasodium pyrophosphate, or a polyphosphate, for example sodiumtripolyphosphate. These polyphosphates may be used alone or in anycombination thereof.

An effective amount of a polyphosphate source may be from about 0.1% toabout 30%, preferably from about 1% to about 26%, more preferably fromabout 4% to about 20%, and most preferably from about 5% to about 13%,by weight of the total dentifrice composition. A typical range is fromabout 1% to about 10% by weight of the total dentifrice composition,more typically from about 3% to about 7% by weight of the totaldentifrice composition.

Aqueous Carriers

In preparing the present compositions, it is desirable to add one ormore aqueous carriers to the compositions. Such materials are well knownin the art and are readily chosen by one skilled in the art based on thephysical and aesthetic properties desired for the compositions beingprepared. Aqueous carriers typically comprise from about 40% to about99%, preferably from about 70% to about 98%, and more preferably fromabout 90% to about 95%, by weight of the dentifrice composition.

Total Water Content

Water employed in the preparation of commercially suitable oralcompositions should preferably be of low ion content and free of organicimpurities. In the dentifrice composition, water will generally compriseless than about 10%, and preferably front about 0% to about 6%, byweight of the composition herein. Polyphosphate and actives such asfluoride and stannous are not dissolved in the compositions herein insuch low levels of water. However, these ingredients may be dissolved inthe present compositions in other low polar solvents, forming non-ionicmolecular structures. In either case, the actives remain stable in thecompositions during storage. The fluoride ion and the stannous ion ifpresent will be released from their salt forms or non-ionic solutionforms when contacted with saliva and/or water at the time of brushing.Titus there is no need to physically separate thepolyphosphate-containing portion of the composition from the ionicactive-containing portion of the composition, for example by using adual compartmented package. In addition, fluoride ion from a variety ofsources may be used efficaciously in the present composition; there isno preference for the use of sodium monofluorophosphate as the fluorideion source that is most compatible with the polyphosphate in thecomposition as previously described in U.S. Pat. No. 6,190,644,“Dentifrice Compositions Containing Polyphosphate and SodiumMonofluorophosphate.”

The amounts of water include the free water that is added plus thatwhich is introduced with other materials, such as with silica,surfactant solutions, and/or color solutions.

Binder System

The dentifrice compositions of the present invention preferablyincorporate a binder system incorporating a cross-linkedpolyvinylpyrrolidone in combination with a gum. The binder system mayfurther incorporate at least one additional thickening agent selectedfrom the group consisting of polysaccharides, carbomers, poloxamers,modified celluloses, and mixtures thereof, and at least one humectant.The thickening agent comprises from about 0.05% to about 3%, andpreferably from about 0.1% to 1.5%, by weight of the composition. Thesebinder systems provide desirable consistency and gellation to the lowwater composition. It has previously been known that gelling materialsthat provide desirable rheology with water and humectant providegenerally less satisfactory rheology when the water is not present toactivate their gellation binding properties. This is believed to beespecially true of glycerin humectant. The binder system may furthercomprise additional inorganic thickening agents.

Thickening Agent

Polysaccharides, including gums, that are suitable for use hereininclude carageenans, gellan gum, locust bean gum, xanthan gum, andmixtures thereof. Carageenan is a polysaccharide derived from seaweedand has been known for use as a binder or thickener in toothpastes, see,e.g., U.S. Pat. Nos. 6,187,293 B1 and 6,162,418. There are several typesof carageenan that may be distinguished by their seaweed source and/orby their degree of and position of sulfation. Suitable for use in thepresent invention are kappa carageenans, modified kappa carageenans,iota carageenans, modified iota carageenans, and mixtures thereof.Carageenans suitable for use herein include those commercially availablefrom the FMC Company under the series designation “Viscarin,” includingbut not limited to Viscarin TP 329, Viscarin TP 388, and Viscarin TP389.

Gellan gum is another polysaccharide that is suitable for use herein. Itis a polysaccharide aerobically fermented by pseudomonas elodea. It canalso form an acceptable low water matrix when it is present at a levelof from about 0.4% to about 3%, preferably from about 0.4% to about 1.8%(w/w).

Locust bean gum and xanthan gum are also suitable polysaccharides foruse herein. Locust bean gum or xanthan gum as thickening agents can forma stable and acceptable dentifrice matrix when water level is lower than10% in the composition.

Poloxamers are also suitable as thickening agents in the low watermatrix herein. Poloxamer is a synthetic block copolymer of ethyleneoxide and propylene oxide. It is available in several types. Herein,poloxamer 407 is preferable. It can be partly dissolved in water. Whentemperature is higher than 65° C., it can dissolve in glycerin.POLOXAMER 407® is available, for example, from the BASF CORPORATION, NewJersey, USA.

Carbomers are also suitable as thickening agents in a low water matrix,especially in non-water matrix.

Modified celluloses such as hydroxyethyl cellulose are also goodthickening agents in low water matrix. Since the water level is limitedin the present compositions, modified hydroxyethyl cellulose with ahydrophobic chain (C₁₂-C₂₀) are preferred to increase the solubility andhydration of this thickening agent in other low polar solvents, such asglycerin, propylene glycol and PEG.

Humectant

The humectant serves to keep toothpaste compositions from hardening uponexposure to air and certain humectants can also impart desirablesweetness of flavor to toothpaste compositions. Suitable humectants foruse in the invention include glycerin, sorbitol, polyethylene glycol,propylene glycol, xylitol, and other edible polyhydric alcohols.Preferred are glycerin, polyethylene glycol, polypropylene glycol, andmixtures thereof, especially mixtures thereof. The humectant generallycomprises from about 0.1% to 70%, preferably from about 1% to about 60%,and more preferably from about 15% to 55%, by weight of the composition.

The humectant is believed to have a significant impact on the viscosityof the low water matrix. For example, when using polysaccharide as thethickening agent in the composition, the viscosity of the matrix willincrease when the level of glycerin or polyethylene glycol increases. Onthe contrary, the viscosity of matrix will decrease when the level ofpropylene glycol increases in the composition.

Inorganic Thickening Agents

The binder system may further comprise additional inorganic thickeningagents such as colloidal magnesium aluminum silicate or finely dividedsilica to further improve texture. Additional inorganic thickeningagents if present can be used in an amount from about 0.1% to about 15%,more preferably from about 0.1% to about 5%, by weight of the dentifricecomposition.

Ionic Active Ingredient

The dentifrice compositions of the present invention preferably comprisean effective amount of an ionic active ingredient selected from thegroup consisting of a fluoride ion source, a stannous ion source, a zincion source, and mixtures thereof.

Fluoride Ion Source

The fluoride ion source herein is a soluble fluoride source capable ofproviding free fluoride ions. Soluble fluoride ion sources includesodium fluoride, stannous fluoride, indium fluoride, zinc fluoride, andsodium monofluorophosphate. Sodium fluoride and stannous fluoride arethe preferred soluble fluoride ion sources. Norris et al., U.S. Pat. No.2,946,725, issued Jul. 26, 1960, and Widder et al., U.S. Pat. No.3,678,154 issued Jul. 18, 1972, disclose such fluoride ion sources aswell as others.

The fluoride ion source in the present compositions preferably ispresent as a solid dispersion in the composition during storage, priorto actual brushing usage of the composition by a consumer. The level ofwater in the present compositions is too low to permit the fluoridesource to dissolve in the composition during storage. Thus, there is noobvious interaction between the fluoride ion and the polyphosphate, orsilica if present, during storage, providing a stable composition duringstorage. When the composition is contacted by saliva and/or water at thetime of brushing, the fluoride source preferably will be dispersed andthe active ion will be delivered to the oral cavity.

The present compositions may contain a soluble fluoride ion sourcecapable of providing front about 50 ppm to about 3500 ppm, andpreferably from about 500 ppm to about 3000 ppm of free fluoride ions.To deliver the desired amount of fluoride ions, fluoride ion source maybe present in the total dentifrice composition at an amount of fromabout 0.1% to about 5%, preferably from about 0.2% to about 1%, and morepreferably from about 0.3 to about 0.6%, by weight of the totaldentifrice composition.

Metal Ion Source

The present invention may comprise a metal ion source that providesstannous ions, zinc ions, or mixtures thereof. The metal ion source canbe a soluble or a sparingly soluble compound of stannous or zinc withinorganic or organic counter ions. Examples include the fluoride,chloride, chlorofluoride, acetate, hexafluorozirconate, sulfate,tartrate, gluconate, citrate, malate, glycinate, pyrophosphate,metaphosphate, oxalate, phosphate, carbonate salts and oxides ofstannous and zinc.

Stannous and zinc ions have been found to help in the reduction ofgingivitis, plaque, sensitivity, and improved breath benefits. Theefficacy of these metal ions in the present compositions is not reducedby the polyphosphate.

Stannous and zinc ions are derived from the metal ion source(s) found inthe dentifrice composition in an effective amount. An effective amountis defined as from at least about 1000 ppm metal ion, preferably about2,000 ppm to about 15,000 ppm. More preferably, metal ions are presentin an amount from about 3,000 ppm to a bout 13,000 ppm and even morepreferably from about 4,000 ppm to about 10,000 ppm. This is the totalamount of metal ions (stannous and zinc and mixtures thereof) that ispresent in the compositions for delivery to the tooth surface.

The metal ion sources in the present compositions are preferably notfully ionized in the composition during storage, prior to actualbrushing usage of the composition by a consumer. The level of water inthe present compositions is too low to permit the metal ion source todissolve in the composition during storage. But certain salts such asstannous chloride and stannous fluoride, can be solubilized in glycerinor propylene glycol. Both humectants can provide super stabilityprotection for such stannous salts and also can provide a better tasteprofile than a water (aqueous) solution of stannous. When thecomposition is contacted by saliva and/or water at the time of brushing,the stannous ion source will be fully ionized and the active ion will bedelivered to the oral cavity.

Dentifrices containing stannous salts, particularly stannous fluorideand stannous chloride, are described in U.S. Pat. No. 5,004,597 toMajeti et al. Other descriptions of stannous salt dentifrices are foundin U.S. Pat. No. 5,578,293. The preferred stannous salts are stannousfluoride and stannous chloride dihydrate. Other suitable stannous saltsinclude stannous acetate, stannous tartrate and sodium stannous citrate.Examples of suitable zinc ion sources are zinc oxide, zinc sulfate, zincchloride, zinc citrate, zinc lactate, zinc gluconate, zinc malate, zinctartrate, zinc carbonate, zinc phosphate, and other salts listed in U.S.Pat. No. 4,022,880.

The combined metal ion source(s) will be present in an amount of fromabout 0.25% to about 11%, by weight of the final composition.Preferably, the metal ion sources are present in an amount of from about0.4 to about 7%, more preferably from about 0.45% to about 5%.

Buffering Agent

The compositions described herein also may contain a buffering agent inaddition to the chelating buffer agent for the stannous ions that isused in a premix as described hereinabove. Buffering agents, as usedherein, refer to agents that can be used to adjust the pH of thecompositions to a range of about pH 3.0 to about pH 10. The phase of thedentifrice containing stannous will typically have a slurry pH of fromabout 3.0 to about 5.5, preferably from about 3.25 to about 5, and morepreferably from about 3.4 to about 4.5. The phase of the dentifricecontaining the polyphosphate will typically have a slurry pH of fromabout 4.0 to about 10, preferably from about 4.5 to about 8, and morepreferably from about 5.0 to about 7.0. A dentifrice containing bothstannous and polyphosphate in a single phase will typically have a pH offrom about 4 to about 7, preferably from about 4.5 to about 6, and morepreferably from about 5 to about 5.5.

The buffering agents include alkali metal hydroxides, ammoniumhydroxide, organic ammonium compounds, carbonates, sesquicarbonates,borates, silicates, phosphates, imidazole, and mixtures thereof.Specific buffering agents include monosodium phosphate, trisodiumphosphate, sodium benzoate, benzoic acid, sodium hydroxide, potassiumhydroxide, alkali metal carbonate salts, sodium carbonate, imidazole,pyrophosphate salts, citric acid, and sodium citrate. Buffering agentsare used at a level of from about 0.1% to about 30%, preferably fromabout 0.1% to about 10%, and more preferably from about 0.3% to about3%, by weight of the present composition. When stannous is present inthe composition, preferred buffers are sodium hydroxide, potassiumhydroxide, and ammonium hydroxide.

Anticalculus Agents

The compositions described herein also may employ, as anticalculusagents, polyphosphate materials known to be effective in reducingcalcium phosphate mineral deposition related to calculus formation.Agents included are pyrophosphates, and tripolyphosphates. Thecompositions may also employ synthetic anionic polymers [includingpolyacrylates and copolymers of maleic anhydride or acid and methylvinyl ether (e.g., GANTREZ®), as described, for example, in U.S. Pat.No. 4,627,977 to Gaffar et al.; as well as, e.g., polyamino propanesulfonic acid (AMPS)], zinc citrate trihydrate, diphosphonates (e.g.,EHDP; AHP), polypeptides polyaspartic and polyglutamic acids), andmixtures thereof.

Abrasive Polishing Materials

An abrasive polishing material may also be included in the toothpastecompositions. The abrasive polishing material contemplated for use inthe compositions of the present invention can be any material that doesnot excessively abrade dentin. Typical abrasive polishing materialsinclude silicas including gels and precipitates; aluminas; phosphatesincluding orthophosphates, polymetaphosphates, and pyrophosphates; andmixtures thereof. Specific examples include dicalcium orthophosphatedihydrate, calcium pyrophosphate, tricalcium phosphate, calciumpolymetaphosphate, insoluble sodium polymetaphosphate, hydrated alumina,beta calcium pyrophosphate, calcium carbonate, and resinous abrasivematerials such as particulate condensation products of urea andformaldehyde, and others such as disclosed by Cooley et al in U.S. Pat.No. 3,070,510, issued Dec. 25, 1962. Mixtures of abrasives may also be,used. If the dentifrice composition or particular phase comprises apolyphosphate having an average chain length of about 4 or more, calciumcontaining abrasives and alumina are not preferred abrasives. The mostpreferred abrasive is silica.

Silica dental abrasives of various types are preferred because of theirunique benefits of exceptional dental cleaning and polishing performancewithout unduly abrading tooth enamel or dentine. The silica abrasivepolishing materials herein, as well as other abrasives, generally havean average particle size ranging between about 0.1 to about 30 microns,and preferably from about 5 to about 15 microns. The abrasive can beprecipitated silica or silica gels such as the silica xerogels describedin Pader et al., U.S. Pat. No. 3,538,230, issued Mar. 2, 1970, andDiGiulio, U.S. Pat. No. 3,862,307, issued Jan. 21, 1975. Preferred arethe silica xerogels marketed under the trade name “SYLOID®” by the W. R.Grace & Company, Davison Chemical Division. Also preferred are theprecipitated silica materials such as those marketed by the J. M. HuberCorporation under the trade name, “ZEODENT®”, particularly the silicacarrying the designation “Zeodent 119.” The types of silica dentalabrasives useful in the toothpastes of the present invention aredescribed in more detail in Wason, U.S. Pat. No. 4,340,583, issued Jul.29, 1982. Silica abrasives are also described in Rice, U.S. Pat. Nos.5,589,160; 5,603,920; 5,651,958; 5,658,553; and 5,716,601. The abrasivein the toothpaste compositions described herein is generally present ata level of from about 6% to about 70% by weight of the composition.Preferably, toothpastes contain from about 10% to about 50% of abrasive,by weight of the dentifrice composition.

Peroxide Source

The present invention may include a peroxide source in the composition.The peroxide source is selected from the group consisting of hydrogenperoxide, calcium peroxide, urea peroxide, and mixtures thereof. Thepreferred peroxide source is calcium peroxide. The following amountsrepresent the amount of peroxide raw material, although the peroxidesource may contain ingredients other than the peroxide raw material. Thepresent composition may contain from about 0.01% to about 10%,preferably from about 0.1% to about 5%, more preferably from about 0.2%to about 3%, and most preferably from about 0.3% to about 0.8% of aperoxide source, by weight of the dentifrice composition.

Alkali Metal Bicarbonate Salt

The compositions also may include an alkali metal bicarbonate salt.Alkali metal bicarbonate salts are soluble in water and unlessstabilized, tend to release carbon dioxide in an aqueous system. Sodiumbicarbonate, also known as baking soda, is the preferred alkali metalbicarbonate salt. The alkali metal bicarbonate salt also functions as abuffering agent. The present composition may contain from about 0.5% toabout 50%, preferably from about 0.5% to about 30%, more preferably fromabout 2% to about 20%, and most preferably from about 5% to about 18% ofan alkali metal bicarbonate salt, by weight of the dentifricecomposition.

Additional Aqueous Carriers

The compositions also may comprise surfactants, also commonly referredto as sudsing agents. Suitable surfactants are those that are reasonablystable and foam throughout a wide pH range. The surfactant may beanionic, nonionic, amphoteric, zwitterionic cationic, or mixturesthereof. Anionic surfactants useful herein include the water-solublesalts of alkyl sulfates having from 8 to 20 carbon atoms in the alkylradical (e.g., sodium alkyl sulfate) and the water-soluble salts ofsulfonated monoglycerides of fatty acids having from 8 to 20 carbonatoms. Sodium lauryl sulfate and sodium coconut monoglyceride sulfonatesare examples of anionic surfactants of this type. Other suitable anionicsurfactants are sarcosinates, such as sodium lauroyl sarcosinate,taurates, sodium lauryl sulfoacetate, sodium lauroyl isethionate, sodiumlaureth carboxylate, and sodium dodecyl benzenesulfonate. Mixtures ofanionic surfactants can also be employed. Many suitable anionicsurfactants are disclosed by Agricola et al., U.S. Pat. No. 3,959,458,issued May 25, 1976.

Nonionic surfactants that can be used in the compositions can broadly bedefined as compounds produced by the condensation of alkylene oxidegroups (hydrophilic in nature) with an organic hydrophobic compoundwhich may be aliphatic or alkyl-aromatic in nature. Examples of suitablenonionic surfactants include poloxainers (sold under trade namePLURONIC®), polyoxyethylene, polyoxyethylene sorbitan esters (sold undertrade name TWEENS®), Polyoxyl 40 hydrogenated castor oil, fatty alcoholethoxylates, polyethylene oxide condensates of alkyl phenols, productsderived from the condensation of ethylene oxide with the reactionproduct of propylene oxide and ethylene diamine, ethylene oxidecondensates of aliphatic alcohols, long chain tertiary amine oxides,long chain tertiary phosphine oxides, long chain dialkyl sulfoxides, andmixtures of such materials. The amphoteric surfactants useful in thepresent invention can be broadly described as derivatives of aliphaticsecondary and tertiary amines in which the aliphatic radical can be astraight chain or branched and wherein one of the aliphatic substituentscontains from about 8 to about 18 carbon atoms and one contains ananionic water-solubilizing group, e.g., carboxylate, sulfonate, sulfate,phosphate, or phosphonate. Other suitable amphoteric surfactants arebetaines, specifically cocamidopropyl betaine. Mixtures of amphotericsurfactants can also be employed. Many of these suitable nonionic andamphoteric surfactants are disclosed by Gieske et al. in U.S. Pat. No.4,051,234. The present composition typically comprises one or moresurfactants each at a level of from about 0.25% to about 12%, preferablyfrom about 0.5% to about 8%, and most preferably from about 1% to about6%, by weight of the composition.

Titanium dioxide may also be added to the present composition. Titaniumdioxide is a white powder which adds opacity to the compositions.Titanium dioxide generally comprises from about 0.25% to about 5%, byweight of the composition.

Coloring agents may also be added to the present composition. Thecoloring agent may be in the form of an aqueous solution, preferably 1%coloring agent in a solution of water. Color solutions generallycomprise from about 0.01% to about 5%, by weight of the composition.

A flavor system can also be added to the compositions. Suitableflavoring components include oil of wintergreen, oil of peppermint, oilof spearmint, clove bud oil, menthol, anethole, methyl salicylate,eucalyptol, cassia, 1-menthyl acetate, sage, eugenol, parsley oil,oxanone, alpha-irisone, marjoram, lemon, orange, propenyl guaethol,cinnamon, vanillin, ethyl vanillin, heliotropine, 4-cis-heptenal,diacetyl, methyl-para-tert-butyl phenyl acetate, and mixtures thereof.Coolants may also be part of the flavor system. Preferred coolants inthe present compositions are the paramenthan carboxyamide agents such asN-ethyl-p-menthan-3-cathoxamide (known commercially as “WS-3”) andmixtures thereof. A flavor system is generally used in the compositionsat levels of from about 0.001% to about 5%, by weight of thecomposition.

Sweetening agents can be added to the compositions. These includesaccharin, dextrose, sucrose, lactose, xylitol, maltose, levulose,aspartame, sodium cyclamate, D-tryptophan, dihydrochalcones, acesulfame,and mixtures thereof. Various coloring agents may also be incorporatedin the present invention. Sweetening agents and coloring agents aregenerally used in toothpastes at levels of from about 0.005% to about5%, by weight of the composition.

The present invention may also include other agents, such asantimicrobial agents. Included among such agents are water insolublenon-cationic antimicrobial agents such as halogenated diphenyl ethers,phenolic compounds including phenol and its homologs, mono andpoly-alkyl and aromatic halophenols, resorcinol and its derivatives,bisphenolic compounds and halogenated salicylanilides, benzoic esters,and halogenated carbanilides, polyphenols, and herbals. The watersoluble antimicrobials include quaternary ammonium salts andbis-biquanide salts, among others. Triclosan monophosphate is apreferred additional water soluble antimicrobial agent. The quaternaryammonium agents include those in which one or two of the substitutes onthe quaternary nitrogen has a carbon chain length (typically alkylgroup) from about 8 to about 20, typically from about 10 to about 18carbon atoms while the remaining substitutes (typically alkyl or benzylgroup) have a lower number of carbon atoms, such as from about 1 toabout 7 carbon atoms, typically methyl or ethyl groups. Dodecyltrimethyl ammonium bromide, tetradecylpyridinium chloride, domiphenbromide, N-tetradecyl-4-ethyl pyridinium chloride, dodecyl dimethyl(2-phenoxyethyl) ammonium bromide, benzyl dimethylstearyl ammoniumchloride, cetyl pyridinium chloride, quaternized5-amino-1,3-bis(2-ethyl-hexyl)-5-methyl hexa hydropyrimidine,benzalkonium chloride, benzethonium chloride and methyl benzethoniumchloride are examplary of typical quaternary ammonium antibacterialagents. Other compounds are bis[4-(R-amino)-1-pyridinium] alkanes asdisclosed in U.S. Pat. No. 4,206,215, issued Jun. 3, 1980, to Bailey.

Other antimicrobials such as copper bisglycinate, copper glycinate, zinccitrate, and zinc lactate may also be included. Also useful are enzymes,including endoglycosidase, papain, dextranase, mutanase, and mixturesthereof. Such agents are disclosed in U.S. Pat. No. 2,946,725, Jul. 26,1960, to Norris et al. and in U.S. Pat. No. 4,051,234, Sep. 27, 1977 toGieske et al. Specific antimicrobial agents include chlorhexidine,triclosan, triclosan monophosphate, and flavor oils such as thymol.Triclosan is a preferred antimicrobial agent for inclusion in thepresent compositions. Triclosan and other agents of this type aredisclosed in Parran, Jr. et al., U.S. Pat. No. 5,015,466, issued May 14,1991, and U.S. Pat. No. 4,894,220, Jan. 16, 1990 to Nabi et al. Thewater insoluble antimicrobial agents, water soluble agents, and enzymesmay be present in either the first or second dentifrice compositions.The quaternary ammonium agents, stannous salts, and substitutedguanidines are preferably present in the second dentifrice composition.These agents may be present at levels of from about 0.01% to about 1.5%,by weight of the dentifrice composition.

A herbal agent, including but not limited to, golden thread extract,honeysuckle extract, and mixtures thereof, may also be present in thecompositions herein at levels of from about 0.01% to about 0.05%. Suchherbal agents are believed to provide anti-bacterial efficacy.Potyphenols may further be included at levels from about 0.01% to about2%. A preferred polyphenol is tea polyphenol.

An effective amount of a desensitizing agent may also be incorporatedinto the present compositions. The desensitizing agents include thoseselected from alkaline metal salts with a chloride, nitrate sulfate, oracetate of a group II metal or aluminum or polymerizable monomer toocclude the tubules, alkaline metal or ammonium nitrate, ammoniumoxylate, citric acid and sodium citrate. Preferred salts are potassiumnitrate, potassium citrate, and mixtures thereof. Such desensitizingagents are disclosed in e.g., U.S. Pat. No. 5,718,885.

For compositions that contain stannous, a stain reducing agent such asPlasdone 5-630 or aluminum hydrate may further be added to thecomposition. Plasdone is polyvinyl pyrrolidone (PVP) that can besynthesized by polymerizing vinvlpvrrolidone. Commercially, it has beenproduced as a series of products having mean molecular weights rangingfrom 10,000 to 700,000. Herein, the low molecular weights and middlemolecular weights (from about 10,000 to about 100,000) are preferred. Inorder to remove stain effectively, the level of PVP is preferably fromabout 0.5% to about 10%, more preferably from about 1.0% to about 7.0%,and even more preferably from about 1.5% to about 5.0%.

The dentifrice compositions may be a paste, gel, or any configuration orcombination thereof. A further embodiment of the present inventionincludes dual-phase or multi-phase compositions comprising the presentlow-water compositions as one phase and at least one other separatephase comprising additional dentifrice components to further enhancestability, performance and/or aesthetics of the dentifrice product. Forexample, a dual phase composition may comprise a first phase comprisingthe present low-water composition with polyphosphate and ionic active(s)and a separate second phase comprising additional active agents such asbleaching agents, preferably a peroxide source, or a tooth surfaceconditioning agent to provide improved cleaning, whitening,anti-staining and mouth feel benefits. Examples of tooth conditioningagents are polysiloxanes and modified polysiloxanes, includingdiorganopolysitoxanes such as polydimethylsiloxane (PDMS); alkyl- andalkoxy-dimethicone copolyols such as C₁₂ to C₂₀ alkyl dimethiconecopolyols; and aminoalkylsilicones. These siloxane polymers aredescribed for example in U.S. Pat. Nos. 5,759,523; 6,024,891; 6,123,950;6,019,962; 6,139,823 all assigned to The Procter & Gamble Company.

The dispenser for the dentifrice compositions may be a tube, pump, orany other container suitable for dispensing toothpaste. In a dual phaseoral composition, each oral composition will be contained in aphysically separated compartment of a dispenser and dispensedside-by-side.

Methods of Use

In practicing the embodiments, the user need only apply the dentifricecomposition herein, to the tooth surfaces of a human or animal, in theareas desired, in order to obtain a desired effect, e.g., whitening,breath freshening, caries prevention, pain relief, gum health, tartarcontrol, erosion control, etc. Use of dentifrices to control erosion ofthe tooth surface, or to prevent demineralization, are known anddescribed in, for example, U.S. Pat. No. 6,685,920, the disclosure ofwhich is incorporated by reference herein in its entirety. Thecompositions also may be applied to other oral cavity surfaces, such asthe gingival or mucosal tissues, although it is believed that thebenefits are best achieved when the dentifrice compositions are appliedto the teeth. The dentifrice composition may contact the tooth and/ororal cavity surface either directly, or indirectly, however, it ispreferred that the dentifrice composition be directly applied. Thedentifrice composition may be applied by any means, but is preferablyapplied with a brush or by rinsing with a dentifrice slurry.

The manufacture of the oral composition of the present invention may beaccomplished by any of the various standard techniques for producingsuch compositions. To make a dentifrice, a vehicle may be preparedcontaining humectant, for example, one or more of glycerin, glycerol,sorbitol, and propylene glycol, thickener agents and antibacterial agentsuch as triclosan, and the vehicle and a mixture of anionic andamphoteric surfactants are added, followed by blending in of a polishingagent, as well as fluoride salts, with the pre-mix. Finally, flavoringagent, is admixed and the pH is adjusted to between 6.8 to 7.0.

The following examples are further illustrative of the preferredembodiments, but it is understood that the invention is not limitedthereto.

Example 1

Dentifrice compositions were prepared having the formulations asindicated in Table 1.

TABLE 1 INGREDIENT Formula A Formula B Formula C Formula D Deionizedwater 6.000 6.000 4.000 4.000 Citric acid 0.600 0.160 0.000 0.000Trisodium citrate 3.000 0.810 0.000 0.000 Zinc citrate 2.000 2.000 2.0002.000 Glycerin 7.700 20.000 7.700 14.000 Stannous fluoride 0.454 0.4540.454 0.454 Propylene glycol 7.000 0.000 7.000 7.000 Polyethylene glycol600 5.000 7.000 5.000 9.000 Tetrasodium 2.000 2.000 2.000 2.000pyrophosphate Glycerin 28.846 29.786 32.446 30.846 Sodiumtripolyphosphate 3.000 3.000 3.000 3.000 Sodium CMC 7MF 0.700 0.0000.700 0.700 Sodium CMC 2000S 1.000 0.000 1.000 0.300 Xanthan gum NF0.000 0.250 0.000 0.000 Polyplasdone XL-10 0.000 1.000 0.000 0.000Poloxamer 407 1.000 0.000 1.000 0.000 FD&C blue #1 0.000 0.190 0.0000.000 Sodium saccharin 0.500 0.500 0.500 0.500 Titanium dioxide 0.5000.150 0.500 0.500 Zeodent 115 12.000 12.000 12.000 10.000 Zeodent 1654.000 0.000 6.000 3.000 Zeodent 105 12.000 12.000 12.000 10.000 STPdental cream flavor 1.200 1.200 1.200 1.200 Sodium lauryl sulfate 1.5001.500 1.500 1.500 TOTAL 100.00 100.00 100.00 100.00

Each of the formulations contain 0.454 wt % stannous fluoride, 2 wt %zinc citrate and a polyphosphate anti-tartar control system, comprising2 wt % tetrasodium pyrophosphate and 3 wt % sodium tripolyphosphate(i.e. tetrasodium pyrophosphate and sodium tripolyphosphate in a 2:3weight ratio).

The compositions in accordance with Formula A and Formula B incorporateda citrate buffer system comprising a mixture of citric acid and analkali metal citrate, in particular trisodium citrate. Formula A andFormula B were prepared initially as a premix by dissolving the stannousfluoride in an aqueous solution of citric acid and sodium citrate. Thecitrate ions in the premix chelate the stannous ion thereby preventingor inhibiting precipitation of the stannous salt in the finalcomposition and reducing the chance of forming insoluble inactive tincompounds in the dentifrice composition. The premix was then mixed withthe remaining active constituents and the vehicle of the dentifricecomposition.

Example 2

The dentifrice compositions in accordance with Formula A and Formula Cwere subjected to an accelerated aging study to determine the stabilityof the stannous salt. The dentifrice compositions were subjected to atemperature of 1.05° F. for a period of 4 weeks. The initial and finalamounts of soluble tin, representing the available stannous ion, weremeasured at the beginning and at the end of the test. The results areshown in Table 2.

TABLE 2 Formula A Formula C Initial soluble tin (wt %) 0.33 0.24 Finalsoluble tin (wt %) after 4 weeks at 105° F. 0.31 0.16

Table 2 shows that for the composition of Formula A the initial amountof soluble tin was 0.33 wt % which was reduced to 0.31 wt % at the endof the test, this being a small reduction (about 7%) in stannous tinavailability which is acceptable in a commercial dentifrice.

Table 2 also shows that for the composition of Formula C the initialamount of soluble tin was 0.24 wt % which was reduced to 0.16 wt % atthe end of the test, this being a large reduction (33%) in stannous tinavailability which would not be preferred in a commercial dentifrice.

The citrate buffer system in Formula A accordingly stabilizes thestannous ions when in the presence of zinc ions.

Example 3

The aging study discussed above also investigated the stability of otheractives in the composition of Formulas A and C, and the results areshown in Table 3.

TABLE 3 Ionic Na tripoly Na pyro Na ortho Sol- Sol- Fluo- Phos- Phos-Phos- uble uble ride phate phate phate tin zinc (ppm) (wt %) (wt %) (wt%) (wt %) (wt %) Formula A Initial 985 2.59 2.34 0.14 0.36 0.39 After 4938 2.44 2.1 0.33 0.33 0.39 weeks at 105° F. After 8 1038 2.49 2.16 0.390.33 0.39 weeks at 105° F. After 12 950 2.26 2.11 0.45 0.35 0.34 weeksat 105° F. Formula C Initial 1029 2.86 2.07 none 0.24 0.46 After 4 10082.82 1.80 0.19 0.16 0.42 weeks at 105° F. After 8 1085 2.99 2.24 0.310.15 0.40 weeks at 105° F. After 12 928 2.75 2.13 0.22 0.14 0.45 weeksat 105° F.

Although the soluble tin reduced significantly after 4 weeks for FormulaC, as discussed above, the soluble tin content did not significantlyreduce further up to 12 weeks. The amounts of ionic fluoride, sodiumtripolyphosphate, sodium pyrophosphate (which progressively convertsinto sodium orthophosphate) and soluble zinc remained at acceptablelevels after the 12 week accelerated aging test for both Formula A andC.

Example 4

The composition of Formula C was subjected to an in vitro antibacterialtest in an artificial mouth to measure the antibacterial efficacy of theformulation which comprised the stannous salt and the zinc salt. Theantibacterial efficacy of the formulation was comparable to a commercialdentifrice containing 0.3% Triclosan as an antibacterial component.

Example 5

The formulation of Formula B contained a mixture of a cross-linkedpolyvinylpyrrolidone and a gum, in particular xanthan gum. Moreparticularly the composition included 1 wt % Polyplasdone XL-10 and 0.25wt % xanthan gum.

The formulation was subjected to a rheology test to determine any changein viscosity, resulting from progressive thickening, over time. Inparticular, the composition was subjected to a measurement of Brookfieldviscosity. The viscosities of the composition was determined with aBrookfield Viscometer Model RVT or RVTDV attached to a BrookfieldHelipath Stand utilizing a RV T-Bar Spindle Set. Viscosity profiles wererecorded on a linear 1200 recorder. (Brookfield EngineeringLaboratories, Stoughton, Ma.) Brookfield viscosity of the compositionwas taken at ambient conditions over a period of 14 days and the resultsare shown in FIG. 1. It may be seen that although the Brookfieldviscosity increased substantially (by about 75%) from the initial valueover the period of the test, an acceptable viscosity was maintained overthe period of the test, with the viscosity reaching an acceptable steadystate value after only a few days. The product would be readilydispensable from a container over the expected shelf life of thedentifrice composition.

The Brookfield viscosity of a comparative composition comprising amixture of carboxymethyl cellulose (CMC) as a thickener and across-linked polyvinylpyrrolidone was measured. Specifically, the CMCwas 0.7 wt % CMC 7MF and 0.8 wt % CMC 20005 and the cross-linkedpolyvinylpyrrolidone was 1 wt % Polyplasdone XL-1.0. All otheringredients were the same as for Formula B. The composition wassubjected to the same rheology test over a period of 14 days and theresults are shown in FIG. 2. It may be seen that the Brookfieldviscosity increased substantially (by about 400%) over the period of thetest. This product suffered from the problem of progressive thickening,with the viscosity rapidly becoming too high for easy dispensing of thedentifrice composition from a container. The viscosity did not reach asteady state during the test.

It may be seen therefore that the thickening composition employed inaccordance with the preferred embodiments of the present inventionenabled a rheological steady state to be reached and for any progressivethickening of the dentifrice composition to be reduced or eliminated.

We claim:
 1. A method for the treatment and prevention of bacterialplaque accumulation or prevention of tooth erosion, comprisingadministering to the oral cavity a dentifrice comprising in a singlephase: an orally acceptable vehicle; a source of fluoride ions; a sourceof stannous ions, wherein the source of stannous ions comprises stannousfluoride; a source of zinc ions, wherein the zinc ion source is zinccitrate and/or zinc lactate; and at least one polyphosphate saltselected from the group consisting of inorganic polyphosphate saltswhich have equal to or less than three phosphorous atoms; wherein thedentifrice composition has a total water content of less than about 10%based on the weight of the composition; and the vehicle comprises athickening agent comprising, in combination, a cross-linkedpolyvinylpyrrolidone present in an amount of about 0.75 to 1.25 wt % ofthe composition and xanthan gum present in an amount from about 0.2 to0.3 wt % of the composition.
 2. The method of claim 1, wherein thesource of zinc ions is zinc lactate.
 3. The method of claim 1, whereinthe source of zinc ions is zinc citrate.
 4. The method of claim 1,further comprising an aqueous buffer system for the source of stannousions.
 5. The method of claim 4, wherein the buffer system is adapted tochelate the stannous ions in the composition.
 6. The method of claim 5,wherein the buffer system comprises at least one of an organic acid oran alkali metal salt thereof.
 7. The method of claim 6, wherein theorganic acid is citric acid.
 8. The method of claim 7, wherein thebuffer system comprises a mixture of citric acid and trisodium citrate.9. The method of claim 3 wherein the amount of zinc citrate is about 2%by wt. of the composition.
 10. The method of claim 8 wherein the sourceof zinc ions is zinc citrate in an amount of about 2% by wt. of thecomposition.